An important application of LEO data is the prediction of longshore sand 

 transport rates resulting from waves breaking at an angle to the shoreline. 

 The waves produce a longshore current which, when coupled with the breaking 

 wave turbulence that suspends sediment, transports large quantities of sand 

 along the shore. An empirical equation that relates longshore sand transport 

 with wave conditions is available in the Shore Protection Manual (Ch. 4 in 

 U.S. Army, Corps of Engineers, Coastal Engineering Research Center, 1977) . 

 LEO data can be used in the empirical relationship. Some recent theoretical 

 developments also allow the computation of sand transport based on longshore 

 current velocities collected under the LEO program (see Walton, 1980) , making 

 available two separate, although not completely independent, methods for 

 determining longshore transport rates. Comparisons between two independent 

 program observers at a single LEO site suggest that a better (more consistent) 

 agreement exists between transport rates computed from observations of long- 

 shore current velocity rather than observations of wave height and angle 

 (Schneider and Weggel, 1980) 3 . This is not an unusual result, considering 

 that the computed transport rate is sensitive to small changes in the wave 

 angle that are difficult to quantify visually. Determination of the longshore 

 transport rate from measured current velocity does not rely on this measured 

 wave angle. 



Generally, LEO data are analyzed annually; however, 1 year of data is not 

 usually sufficient to adequately define the coastal environment at a site. 

 Conditions at a site can vary appreciably from year to year and the longer the 

 period of reliable LEO records, the better the description of the physical 

 environment. To be statistically descriptive of a site, observations must be 

 recorded at least 20 days of each month. Observations should be made at the 

 same time each day without regard to tidal stage. An observation should not 

 be omitted simply because a specific schedule cannot be met. 



Although the LEO program provides low-cost data on nearshore waves, long- 

 shore and rip currents, wind conditions and beach conditions, the data may not 

 be as reliable as data obtained from sophisticated recording sensors such as 

 wave gages and current meters. The usefulness of the LEO program is best 

 expressed in the statistical descriptions of the environment, often in areas 

 where no other data exist, and in the inexpensive estimations of longshore 

 transport rates. This report provides the current LEO observers and those 

 establishing new LEO sites with information on equipment, data collection and 

 recording procedures, and general guidelines for site selection. 



1 U.S. ARMY, CORPS OF ENGINEERS, COASTAL ENGINEERING RESEARCH CENTER, Shove 

 Protection Manual, 3d ed., Vols; I, II, and III, Stock No. 008-022-00113-1, 

 U.S. Government Printing Office, Washington, D.C. , 1977, 1,262 pp. 



2 WALT0N, T.L., Jr., "Computation of Longshore Energy using LEO Current 

 Observations," CETA 80-3, U.S. Army, Corps of Engineers, Coastal Engineering 

 Research Center, Fort Belvoir, Va. , Mar. 1980. 



3 SCHNEIDER, C. , and WEGGEL, J.R. , "Visually Observed Wave Data at Point 

 Mugu, California," Proceedings of the 17th Conference on Coastal Engineering, 

 American Society of Civil Engineers, 1980. 



